1. Field of the Invention
The present invention relates to a pointer control method, and a pointing apparatus and a host apparatus therefor, and more particularly, to a pointer control method using ultrasound, and a pointing apparatus and a host apparatus therefor.
2. Description of the Related Art
A host apparatus such as a computer allows a menu displayed on a screen of a display unit to be selected using a pointer. An apparatus to position the pointer over the menu is called a pointing apparatus. Hereinafter, a pointing system will be used to refer to a pointing apparatus and a related host apparatus.
In general, there are two types of pointer control methods: a two-dimensional (2D) control method and a three-dimensional (3D) control method. According to the 2D control method, a signal is sent to the host apparatus only when the pointing apparatus moves along a predetermined plane of the screen, thereby moving the pointer to a desired position within the screen. A mouse connected to a desktop computer is a type of apparatus that is controlled by the 2D control method. That is, moving the mouse on a particular plane, such as the plane of a desk, enables the pointer to move to the desired position. On the other hand, according to the 3D method, the pointer can be moved even though the pointing apparatus moves in a three-dimensional space, not along the plane. For instance, assuming that the screen is parallel to a plane indicated by X and Y axes, the pointer moves to correspond to ΔX and ΔY if the pointing apparatus moves by ΔX, ΔY, and ΔZ at a certain position in a space, which is indicated by the X, Y, and Z axes.
A variety of 3D pointing apparatuses built in remote controllers of the host apparatus, such as a digital TV, are developed in view of commercialization of digital broadcasting. A conventional 3D pointing apparatus detects the position of the pointing apparatus via an inertial sensor, generates information regarding the detected position, and sends the information to a host apparatus, such as a TV. Next, the host apparatus moves the pointer according to the information. Here, the inertial sensor may be a gyrosensor or an acceleration sensor.
A gyrosensor, for instance, perceives a variation in an angle of the pointing apparatus and sends a result as an electric signal to a microcomputer. Then, the microcomputer calculates a variation in the angle of the pointing apparatus using the electric signal and sends a calculated result to the host apparatus via a radio-frequency (RF) module. Next, the host apparatus moves the pointer according to the calculated result.
An acceleration sensor, for instance, perceives an acceleration of the pointing apparatus and sends a result as an electric signal to the microcomputer. Next, the microcomputer calculates a moving distance of the pointing apparatus by calculating and integrating the acceleration of the pointing apparatus with the electric signal and provides the moving distance to the host apparatus via the RF module. Then, the host apparatus receives the moving distance and moves the pointer according to the moving distance.
However, because the pointing apparatus communicates with the host apparatus by wireless communication, the pointing apparatus is prone to being exposed to various ambient conditions. Accordingly, the inertial sensor, which is attached to the pointing apparatus and detects the movement of the pointing apparatus, is vulnerable to the ambient conditions, such as vibration or movement of the pointing apparatus. In particular, the gyrosensor can sensitively detect the variation in the angle of the pointing apparatus but the gyrosensor is insensitive to a linear movement of the pointing apparatus, whereas the acceleration sensor can sensitively detect the linear movement of the pointing apparatus but the acceleration sensor is insensitive to the variation in the angle of the pointing apparatus. Also, the inertial sensor can perceive relative positions of the pointing apparatus such as an original position and a changed position. For this reason, to move the pointer to a desired position with a conventional pointing apparatus having the inertial sensor, a user must learn how to use the pointing apparatus, which can take a considerable amount of time. In particular, to use the pointing apparatus including the acceleration sensor, the moving distance of the pointing apparatus is calculated by perceiving the acceleration of the pointing apparatus and integrating the perceived acceleration twice. However, when integrating the perceived acceleration twice, much time is spent and a number of errors is high, which substantially prevents putting such commercialized products on the market.
Meanwhile, in a case of a handheld device including a remote controller, a discharge period and a weight of a power source, e.g., a battery, are very important factors that determine ease of use. However, the conventional pointing apparatus requires a high capacity from the microcomputer to process the electric signal, which is detected by the inertial sensor, and to send a processed result to a host apparatus. Such operation of the pointing apparatus not only results in a large burden placed on the microcomputer but also increases power consumption, thereby shortening a discharge period or a recharge period of the power source.